Bordry told The Associated Press on Wednesday that the testing concerns several riders who were already under scrutiny for having suspicious urine samples that hinted strongly at EPO usage. The original urine tests, carried out in a Lausanne-based laboratory, had cast a shadow of doubt over several riders but proved inconclusive.
"I have decided that we will retest - with blood testing - all those who showed up as suspicious during the urine samples," Bordry said by telephone. "When we did the urine samples of those athletes, we had a serious suspicion that there was CERA. The laboratory could not say definitively. The same analysis will be done, but in the blood samples."
Bordry ordered the blood samples to be sent back to France for analysis. The tests will be done at the Chatenay-Malabry lab that snared Floyd Landis for testosterone after the 2006 Tour.
"All the blood tests have been repatriated to France," Bordry said, adding that testing began Monday.
Bordry declined to name the cyclists concerned, adding that the AFLD must first inform the riders if they are positive before making any news official.
However, Bordry said the testing will take "10 days, 15 days maximum." That makes it possible that a rider could be informed during the UCI world championships in Varese, Italy, starting Tuesday and ending Sept. 28.
Italian rider Riccardo Ricco already tested positive for CERA during the Tour, and others may follow.
Tour director Christian Prudhomme would not comment, one of his advisers said, while the testing is ongoing.
"It is a matter for the AFLD," spokesman Christophe Marchadier said by telephone.
However, it would be another big blow to cycling if more riders test positive.
Two years ago, the Landis scandal rocked the Tour, and its credibility was almost destroyed in 2007.
After the final mountain stage of the 2007 Tour, Michael Rasmussen held a comfortable lead and looked set to win.
Then, late that night, the Danish rider was removed by his own Rabobank team for lying about his whereabouts when he missed pre-race drug tests. The previous day, Alexandre Vinokourov, Astana's star rider, tested positive for a blood transfusion after winning the stage 13 time trial.
Some sponsors and television companies ended their deals - and others followed suit after this year's Tour.
Prudhomme, however, keeps on insisting that the net is closing in on cheats and that cycling is cleaning itself up.
CERA is relatively new on the market. If the latest tests reveal more positive cases, dopers would be forced to look for a new product they hope will slip under the radar.
Bordry also said Wednesday that Spanish rider Moises Duenas Nevado's "B" sample came back positive for EPO, confirming the original finding.
Also testing positive during this year's Tour were Manuel Beltran of Spain, for EPO, and Dmitriy Fofonov of Kazakhstan, for a banned stimulant.
Ricco and his teammate Leonardo Piepoli were fired by the Saunier Duval team - which also lost its sponsor.
Even though Piepoli did not test positive, he was released for violating the team's ethical code. Spanish media later reported that Piepoli had admitted to his team that he took the same form of EPO as Ricco.
French cyclist Jimmy Casper tested positive for a banned steroid, but has since been cleared on the grounds that he had forgotten to renew a prescription for a long-standing asthma problem.